In theoretical linguistics, grammaticality is the quality of a linguistic utterance of being grammatically well-formed. An * before a form is a mark that the cited form is ungrammatical.
Lyons 1968 defines the concept as "that part of the acceptability of utterances which can be accounted for in terms of the rules", a criterion that complements acceptability for semantic soundness.
Generative linguists think that for native speakers of natural languages, grammaticality is a matter of linguistic intuition, a competence learned by language acquisition in childhood. Therefore, generative linguistics strives to predict grammaticality exhaustively. On the other hand, there is a gradual abandonment of grammaticality in favour of acceptability by linguists that stress the social acquisition of language in contrast to innate factors (and who will seldom rely on phrase structure grammar) in the tradition of Hopper 1987. Prescriptive grammars of controlled natural languages define grammaticality as a matter of explicit consensus.